In ArF immersion lithography and extreme ultraviolet light (EUV) lithography, finer processing size of a resist line width has been required. In the formation of a finer resist pattern, a contact area between the resist pattern and an underlying substrate is decreased to increase the aspect ratio of the resist pattern (height of the resist pattern/line width of the resist pattern). As a result, there is a concern that the resist pattern is likely to collapse. Therefore, in order not to cause the collapse, high adhesion to the resist pattern has been required for a resist underlayer film (anti-reflective coating) that comes into contact with the resist pattern.
In order to exhibit high adhesion to the resist pattern in the resist underlayer film, it is reported that the adhesion to the obtained resist pattern is improved by using a resist underlayer film-forming composition containing a lactone structure (Patent Document 1). That is, when a resist underlayer film-forming composition containing a polar moiety like a lactone structure is used, the adhesion to the resist pattern is improved. Accordingly, prevention of collapse of the resist pattern in the finer resist pattern is expected.
However, in a lithography process that requires the formation of a finer resist pattern, such as ArF immersion lithography and extreme ultraviolet light (EUV) lithography, it cannot be said that only the lactone structure contained in the resist underlayer film-forming composition is sufficient to prevent the collapse of the resist pattern.
In order to achieve high adhesion of the resist underlayer film to the resist pattern, Patent Document 2 describes an additive for a resist underlayer film-forming composition that can suppress a change of skirt shape of the resist pattern into an undercut shape by modifying a surface state of the resist underlayer film into a basic state. Patent Document 3 describes an additive for a resist underlayer film-forming composition that can suppress a change of skirt shape of the resist pattern into a footing shape by segregation of an additive component near the surface of the resist underlayer film.
Patent Document 4 describes a resist underlayer film-forming composition for lithography containing a copolymer having a structural unit in which a sulfo group is introduced into a terminal, a cross-linking agent, and a solvent. The invention described in Patent Document 4 exerts an effect of suppressing the generation of a sublimate derived from a cross-linking catalyst component in the formation of the resist underlayer film, and can provide a resist underlayer film capable of forming a resist pattern of good shape in which the lower portion have almost no footing shape.